Best quasi-direct-drive actuators for legged robots (2026)

By Tolerance Labs engineering team · Updated 13 October 2026

How this list was made. We sell the CubeMars, HighTorque, Keya, Steadywin actuators below. Other makers’ models are included where they compete, and link to their makers. Rankings use the makers’ published specifications, normalized to the same units; we have not bench-tested every model. More on how we write these.

Quasi-direct-drive (QDD) actuators pair a high-torque motor with a single low-ratio planetary stage, 12:1 or less, so the joint stays backdrivable and fast. This is the layout most legged robots use. Below, every QDD actuator we track, ranked by peak torque.

Picks by robot size

• Small quadrupeds and arms under about 10 kg (up to 15 N·m peak): CubeMars AKE60-8 KV80 has the most torque per kilogram (12.5 N·m at 0.26 kg); also consider RobStride RS00 (14 N·m, 0.31 kg) and Steadywin GIM4315-8 (14.25 N·m, 0.34 kg).
• Mid-size quadrupeds and exoskeleton joints (15–40 N·m peak): Steadywin GIM8108-8 has the most torque per kilogram (22 N·m at 0.38 kg); also consider RobStride RS06 (36 N·m, 0.62 kg) and CubeMars AK70-9 V3.0 KV60 (29.2 N·m, 0.54 kg).
• Large quadrupeds and humanoid knees (40–100 N·m peak): RobStride RS03 has the most torque per kilogram (60 N·m at 0.88 kg); also consider Steadywin TT8116-9 (60.07 N·m, 0.95 kg) and Steadywin GIM8115-9 (40 N·m, 0.66 kg).
• Full-size humanoid hips and knees (100 N·m peak and up): CubeMars AKE90-8 KV35 has the most torque per kilogram (170 N·m at 1.4 kg); also consider RobStride RS04 (120 N·m, 1.42 kg).

Every QDD actuator compared

* Housing-less motors (Steadywin WGG and GWK): the published weight leaves out a housing, so torque per kilogram isn’t comparable with housed modules. They are left out of the picks above.

What to look for when buying

• Peak torque for the worst pose, rated torque for standing. Size peak from body weight and leg geometry with the joint torque calculator; rated torque decides whether the joint overheats while the robot stands.
• Torque per kilogram. Leg joints are carried by the robot, so every gram adds torque elsewhere. The table’s N·m/kg column compares this directly.
• Gear ratio. Lower ratios backdrive more easily and handle impacts better; higher ratios give more torque from the same motor. See Backdrivability in robot joints.
• Bus voltage. Pick one voltage for the whole robot. 48 V reaches higher speed at the same current than 24 V.
• Interface and protocol. Most QDD modules talk CAN or CAN FD; check the protocol (MIT mode, CANopen) your controller expects. See CAN, CAN FD, EtherCAT or RS485.
• Encoders. An output-side or dual encoder gives the joint angle directly after the reducer. See Encoders for robot joints.

Browse every model with filters in quasi-direct-drive joints, or compare a line in the CubeMars AK series and the Steadywin GIM series.